Process for the production of galvanic metal coatings



Patented Apr. 3, 1928.

UNITED STATES FELIX KIRSCHNER, OF VIENNA, AUSTRIA.

PROCESS FOR THE PRODUCTION OF GALVANIC METAL COATINGS.

No Drawing. Application filed October 12, 1923,

The present invention relates to a process for the production of galvanic coatings, which is remarkable for the high quality of the goods produced and the economy with which the process can be carried out. It has been found that galvanic coatings which are deposited upon a metallic intermediate coating alloyed to the basic metal of the article, possess surprising qualities as regards appearance, adherence, density, hardness, polish and resistance to chemical and mechanical influences. lVith the new process, new alloy coated goods (galvano-alloyed goods) can be produced and numerous forms of plating which hitherto could only be obtained by means of difficult and costly processes (nickel plating, silver plating and the like) can be effected in a simple manner and of a technically high quality.

One application of the new process 1s described below in connection with the production of galvanic nickel platlng. v

The goods to be nickel plated are for example first galvanically provided with a metal coating of pure .tin or an alloy or alloys containing tin. The intermediate coating of tin or tin alloy thus applied is then fused on by the application of heat and other known means, so that the intermediate layer after hardening has a smooth brlght and glossy surface. During the fusingof the intermediate layer the deposited metal (tin or tin alloy) becomes alloyed with the basic metal (e. g. iron or copper) of the. goods. This intermediate product, having for example a body of iron or copper has a surface of pure deposited metal (tin) with a smooth bright and glossy surface, whilstwhere the deposited metal adjoins the basic metal of the article there is formed an alloy of the basic metal with thetin or tin alloy that has been deposited.

It is particularly advantageous to alloy the galvanically applied intermediate layer (for example tin) with the basic metal and to provide it with a bright and glossy surface in the following manner. The galvanically applied intermediate layer upon the goods is fused with the assistance of known flux agents (for example of dilute acids, ammonium chloride with or without the ad dition of metal salts) and is cooled in a water bath in a manner suited to the speclfic manner of cooling of the fused metal.

Serial No. 668,162, and in Austria June 19, 1923.

If nickel is galvanicall de osited u the intermediate product tl ius (ibtained, i t i found that the nickel coating, without the usual elaborate preparation that is necessary for n1ckel plating (for example, grinding, polish ng, brushing, burnishing and copperng), is immediately obtained with surprismg closeness, adherence and brightness.

It is advantageous to carry out the galvanic nickel plating immediately after the water cooling of the intermediate layer, that is to say whilst the goods are still wet. Particularly good and bright eflects can be obtained 1f the goods, after the hardening of the intermediate fused layer has been effected by cooling and before the galvanic covering coat1ng 1s applied, are submitted to treatmeriit with weak acids, e. g. weak sulphuric ac1 The above described example of the process for nickel plating can be varied in many different ways. Instead of using the galvamcally produced and subsequently fused intermediate layer which is alloyed with the basic metal, any other process such as a dip ping or boiling process known for obtaining the metallic intermediate layer can be employed, wherein the alloying between the basic metal and the intermediate layer is effected by thermic treatment.

The following is a further example of how the invention may be applied for galvanic silver plating, coating with brass or the like.

In this process a metallic intermediate layer of pure tin or tin alloy is applied to the basic metal by any known dipping process, galvanic process or boiling process. This intermediate layer is given a bright surface by being subjected to heat, either from a flame, or from electric resistances or from a source of radiant heat, and it is alloyed with the basic material. Upon this alloyed intermediate layer metallic outer coatings, two or more in number, can with great advantage be successfully applied.

The alloying of the intermediate layer with the basic metal and the production of a smooth and glossy surface can with particular advantage be obtained by fusing the galvanically applied coating of the intermediate layer with the assistance of fluxes such for example as mixtures of weak acids and ammonium chloride with or without the addition of metal salts, the fusing being cooled with'water according to the specific manner of hardening of the fused metal. .In silver plating, nickel is first deposited galvanically upon the glossy surface of the 1ntermediate layer alloyed with the basic metal and silver is afterwards deposited.

It has been found that with the above described process silver goods can be roduced with only a very thin coating of sllver and that they retain their good appearance for a very long time; this appears to be due to the provision of the hard glossy nickel under coating. But even where a heavy coating of silver isapplied to a basic metal that is not white, for example, brass or pinchbeck, the present process is of considerable value.

For applying a coating of brass or pinchbeck, nickel is first of all galvanically applied to the intermediate layer of metal alloyed with the basic metal and thereupon brass or pinchbeck is deposited by means of any known process.

What I claim is:

1. The herein described method of producing a highly lustrous metallic coating upon a metal base, which consists in electrolytically coating the ground metal with a layer of low-meltingoint metal, fusing the layer to the groun metal and thereupon cooling it in a water solution to transform it into a layer having a smooth highly lustrous surface,

and immediately electrolytically depositing 1 nickel thereupon.

2. The herein described method as set forth in claim 1, in which the low-meltingpoint metal consists of tin.

3. In the herein described method as set forth in claim 1, the additional step of electrolytically depositing a further metal upon the nickel coating.

In testimony whereof I aflix my signature.

FELIX KIRSCHNER. 

